TOKYO (Reuters) - Japan's
farm ministry said on Thursday it may slaughter all of the 5,000-some cows
that had been fed meat-and-bone meal (MBM), a day after a second case of
mad cow disease was found in Japan.

Japan in early October banned all MBM imports and the
use of MBM as feed because infected meal was suspected to be the source
of the disease in Japan and elsewhere.

Both cows found with the disease so far had been born
before Japan placed a ban on imports from Europe early this year. The ban
was imposed on imports from Britain in March 1996.

After the first case of the brain-wasting disease was
found in September on a farm in Chiba, near Tokyo, the Health Ministry
has been carrying out tests of slaughtered meat.

But this would be the first time for Japan to
unconditionally
slaughter cows meant for consumption, to be tested for the disease and
later incinerated.

Japan has 4.5 million cows, including dairy cows.

"We haven't decided on this," an agriculture
ministry official said. "The decision is expected to be made next
week."

On Wednesday, the Health Ministry said a five-year-old
Holstein dairy cow in the northern island of Hokkaido had tested positive
for mad cow disease, formally known as bovine spongiform encephalopathy
(BSE).

It was the second case of the disease in Japan after
a Holstein in Chiba tested positive on September 10 in Asia's first
outbreak
of the disease, deepening a health scare that has already turned consumers
away from beef.

TRACING THE ROUTE

The Hokkaido prefectural government on Thursday launched
an investigation into the second case and asked the dairy farmer who had
raised the infected cow not to move his other 77 cattle, a Hokkaido
government
official said.

The second cow was born in the town of Sarufutsu in
northern
Hokkaido, about 200 kilometers from Saroma in northwestern Hokkaido, where
the Chiba cow in the first case was born. The two cows were born nine days
apart, in spring of 1996.

Given the closeness of birth dates and places, the farm
ministry hopes that the route of infection may be traceable by checking
used feed and nutritional supplements. The ministry has not figured out
the source and route of the first case.

The mad cow scare has swept the world's second-largest
economy, slashing beef sales by more than 50 percent and shaking the farm
and food industries. Meat-eaters in Japan turned their eyes to alternatives
such as pork, chicken and fish.

Experts said it may take years before confidence in beef
recovers in Japan.

Shares in Japan's meat processors and restaurant chains
had tumbled since the September outbreak, driving several to cut sales
and profit estimates for this year.

Consumers have so far largely ignored government
assurances
that Japanese beef is safe for consumption, alarming Japan's top meat
suppliers,
the United States and Australia.

No one has died or fallen sick since Japan's first case
was reported.

Scientists believe that eating beef infected with BSE
can cause a variant of Creutzfeldt-Jakob Disease (vCJD), a fatal brain
affliction. In Europe, vCJD has killed about 100 people.